**Core Concept**
Sarcoidosis is a systemic granulomatous disease characterized by the formation of non-necrotizing and non-caseating granulomas in various organs, including lymph nodes. The granulomas in sarcoidosis are formed due to an abnormal immune response to unknown antigens, leading to the accumulation of activated T lymphocytes and the release of cytokines.
**Why the Correct Answer is Right**
The non-necrotizing and non-caseating granulomas in sarcoidosis are composed of tightly packed epithelioid cells, giant cells, and lymphocytes. The lack of necrosis and caseation is a key distinguishing feature from other granulomatous diseases such as tuberculosis. The granulomas in sarcoidosis are also often surrounded by a halo of lymphocytes, which is a characteristic feature of this disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because sarcoidosis typically affects multiple organs, including the lungs, skin, and eyes, whereas the other options are more specific to a single organ or disease process.
**Option B:** This option is incorrect because tuberculosis typically causes caseating granulomas, which are characterized by necrosis and a cheesy appearance.
**Option C:** This option is incorrect because granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis) is a vasculitic disease that affects small vessels and is characterized by necrotizing granulomas.
**Clinical Pearl / High-Yield Fact**
Sarcoidosis is often referred to as a "great imitator" because it can mimic many other diseases, including tuberculosis, lymphoma, and rheumatoid arthritis. A high index of suspicion is necessary to diagnose sarcoidosis, particularly in patients with an abnormal chest radiograph or lymphadenopathy.
**Correct Answer:** C.
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